Heat transfer



'Nov.' 24, T931) v fT. MIIIDGLEY, JR.. ET AL mustn ruud rob. a, 1930 Patented Nev. 24, 1,931

UNITED s'rArEsrA'rENI ycibi-iriay TIIoIIAs IIIDGLEY, m., or wonTIIINGToN, ALBERTI.. IIENiIE, E comimos, AND ROBERT nrIIcNAnY, or DAYTON, omo, Assmnons To FRIGIDAIRE CORPORATION,

oF DAYTON, omo, A coaroaATIoN or DELAWARE HEAT TRANSFER.

Application led February 8, 1930. Serial No: 426,974.

This application relates to the art of transferring heat from one point to another and spciicall to the ant of refrigeration.

Hereto ore, as ar as We are aware, refrig- '5 erants and heat -transfer agents have been .chosen chiefly for their boiling points and' stability inthe refrigerating or heat transfer cycle irrespective of other desirable properties, such as non-inflammability and non-toxicit 'l It is the object of our invention, on the other hand, to provide a process of refrigeration and, generically, a process of heat transfer in which these desirable properties, such as non-inammability and non-"toxicity, are

obtained in combination with the desired boiling points. l

Broadly stated, the part^ of our process which deals with the controlling ofthe properties of the refrigeratingor heat transfer agents consists in replacingy hydrogen by fluorine or other halogen, or both, in aliphatic hydrocarbons in which at least one hydrogen has already been replaced by luorine.

Broadly stated, the part of our process which relates to the transferof heat or the production of refrigeration comprises chang` ing the physical state of, for example, by condensing or evaporating, a lialo-luoro derivative of an aliphatic hydrocarbon, and dissipating to, or withdrawing from, anobject to be heated or cooled, the latent heat necessary for changing the physical state of the saidderivative. By, a halo-Huoro derivative of an aliphatic hydrocarbon We mean a derivative 1 containing more than one iuorine atom with or without other halogen atoms, or one fiuor-y ine atomrwith one atoms. v

vReterringnow specifically to our mode of controlling the properties of therefrigerating or heat transfer agent, aliphatic 'monofluorides form the structural nucleus on which the agents are built. Broadly speaking, if in the structural formula CHEF we increaseI the fiuorineconten't (number of atoms) by the substitution of iiuorine for hydrogen, the boiling point decreases, stability increases, inliammability decreases, and toxicity decreases. If we keep the fluorine content conor more other halogen mined by applying the boiling l RElSSUED stant and substitute another halogen for hydrogen in the nucleus, the boilingpoint increases, the stability decreases, thetoxicity increases, and the inflammability decreases. The degree to which these variations take place depends on what the other halogen (chlorine, bromine, or iodine) is. As the ratio of the halogen content to the hydrogen content increases the inflammability decreases.'

Because there are several variables, and because of the value of relative proportions, We have placed the compounds of the' group discussed on plots wherein f 't Y Fig. l--is a plot applying the rules of substitution to typical groups having one carbon atom, I

Fig. 2 is a plot applying the rules to groups having two carbon atoms, and i Fig. 3 is a key to Fig. 2, showing the radicals corresponding to the numbers used in 10 eferring to theplots generally,` the dashed lines indicate fiuorine substitutions,- and the solid lines indicate chlorine substitutions. Similar plotsare obtained with bromine and iodine in` place of chlorine except that 'the4 plot is elongated in the direction of higher temperatures with bi'omine, while with iodine t the temperatures are still more elevated. The'amount' of elongation is readily deterpoints of some of these compounds.

Referringspecifically to Fig. 1, this vplot contains all the compounds which can bederived from CH3F by chlorine and/or fluorine substitutions, together withdata which assist in the formation ofthe plot. 'On the base line appear-the'numerals zero to four which show halogen content, and thevertical line gives the approximate boiling points in degrees centigrade. At each point of intersection is given the chlorine and fluorine'content and' the complete formula of the corresponding compound is found by making thisl halogen substitution for hydrogenV in the formula CH4. We have drawn a horizontal dashed lineat about 25" centigrade to indicate approxynately the optimum vapor pressure conditions which We desire for operating an air cooled refrigerator. It is obvious that one to obtain the most desirable rocess of refrigeration under a given set o conditions.

las

In Figure 2 we have shown the same mode of controlling the properties 'of a refrigerant carried to compounds of the same type as in Figure 1 but having two carbon atoms. The key to the chart is given in Fig. 3. For example compound O.1 vis CH3.CH2F, compound 2.9 is CHF2-CC12F, compound 1.5 is CILECHClZ, and vcompound 2.2 is CHFTCHFZ. When we choose as our nucleus a compound having two or more carbons atoms we find that the structural formula gives a choice as to where the substitutions of the halogens shall be made. For example, the structural.

formula of C2H5F is CH3-(ELF, which has a boiling point at about 32 C. If we ina-ke a fluorine substitution for hydrogen in the second radical of this'structural formula so that it reads CHs CHF2 we have a refrigeratin agent whose boiling point is about 45 C. f we make the iuorine substitution for hydrogen onto the other carbon atom so that the formula reads CH2F-CH2F the boiliig point of this refrigerant is about #22 This illustrates the general rule that theiiuorine substitution for hydrogen onto a carbon atom already linked to a halogen lowers the boiling poi'nt, whereas the iuorine substitution for hydrogen onto a carbon atom not already linked to a halogen raises the boiling point. The substitution of chlorine, bromine -or iodine for h drogen raises the boiling point, but the su stitution iny a .radical which 'does not already contain a halogen raises the boilin point more than when the substitution is ma e in a radical which already contains a halogen.

The plot may be expanded in like manner with other aliphatic mono-fluorides. As the number of carbon atoms increases the complexity and extent ofthe lot will increase together with the number o halogens present. These halogen derivatives of aliphatic mono luorides may be represented by the formula CJ'ImFQr in which Y 'C represents carbnand 'n the number of carbon atomsin the molecule which is always equal 'to one or more.

' lH represents hydrogen and m the number of atoms thereof, which lmay equal zero and still fulfill the requirements of our invention.

F represents iuorine and p the number of atoms thereof which is always equal to one or more.

Xrepresents chlorine, bromine or iodine or combinations thereof and r the total number of such atoms. 1 may be zero when p is greater than one. i

Among the chemical groups that these refrigerants fall in are halogen derivatives of aliphatic mono fluorides, halogen derivatives of alkyl mono fluorides, aliphatic luoro halides, alkyl fluoro halides, fluoro derivatives of methyl fluoride, iiuoro halo derivatives of methane and iuoro chloro derivatives of methane.

Thus by our mode of making fluorine and/ or other halogen substitution in a monoiiuoride, we can meet any conditions of refrigeration and provide our refrigerant with the'desired properties, such as non-toxicity and non-inflammability, along with such properties as stability and proper boiling points. l

Referring more'specifically to the part of our process which relates to the actual transfer of heat, we accomplish this transfer of heat by changing the physicall state, of the refrigerant, forjeXample, b'yfcondensing or evaporatingl our aliphatic hydrocarbon derivative which contains more than one fluorine atom with or without other halogen atomsor one fluorine atom with one or more other halogen atoms, and by dissipating to or withdrawing from an .object to be heated or cooled, the heat necessary for the change in physical state. More specifically, to produce refrigeration, we may evaporate the desired derivative in the vicinity of a body to be cooled, while if a heating effect is desired, we may condense the derivative in the vicinit of a body to, be heated, it being understoo of course, that the terms evaporation and condensation separation of a gas from7 and the absorption of a gas in, an absorbent respectively.

Our invention will probably find its greatest utility by adjusting .both the mode of preparing the refrigerant to obtain desirable characteristics andthe mode -of using the refrigerant to obtain a rocess of refrigeration or heat transfer w ich meets the limitations imposed.' We prefer to employ refri erants boiling above C..

bviously our invention is not. limited in its application to any specific form of apparatus for. carrying out the mode of operation described and it will not be necessary for a complete understanding of the invention to show a specific embodiment of apparatus. Nor is the present invention limited to the examples set forth for a particular advance fof the present invention resides in the fact that a great number of new refrigerants with graduated properties is rendered available, and that one is accordingly enabled to secure include the i body to be cooled.

assaut the most suitable refrigerant for varied purposes. l

We claim l 1.. The process of refrigeration which comprisesl condensing a halogen derivative of an aliphatic mono fluoride and then evaporating the said derivative in the vicinity of a body vto beI cooled.

2. The process of refrigeration which comprises condensing a halogen derivative of an alkyl mono fluoride and vthen evaporating the said derivative in the vicinity of a body to be cooled.

3. The process of refrigeration which comprises condensing a halogen derivative of methyl fluoride and then evaporating the said derivative in the vicinity of a body to be cooled. s

4. The process'of refrigeration which comprises condensing a fluoro-halo derivative of methane and then evaporating the said derivative in the vicinity of a body to be cooled.

5.- The process of refrigeration whichv comprises cond-ensing a iluoro-chloro derivative of methane and then evaporating the said vderivative in the vicinity of a body to be cooled.

6. The `process of refrigeration which comprises condensing diiuoro-dichloro'methane and then evaporating it in the vicinity of-a 7 The process of refrigeration which comprises condensing a fluoro halo derivative of an aliphatic hydrocarbon and then evaporating the said derivative inthe vicinity of a body to be cooled.

v8. The process which comprisesvsubstituting halogen for hydrogen 1n an aliphatic' m'onoiluoridev to thereby obtain a. heat transfer agenthaving predetermined requirements of vapor pressure, toxicity, and inflammability, evaporating the heat transfer agent and condensing the evaporated a'gent.

9. The process which comprises substituting halogen for hydrogen 1n an aliphatic monoluoride to thereby obtain a'refrigerant having predetermined requirements of vapor pressure, toxicity, and inviammability, evaporating the said refrigerant and condensing the eva orated refri erant.

10. he process o roducing refrigeration which comprises con ensin a fiuoro-chloro derivativeof an aliphatic ydrocarbon and .then evaporating the ysaid derivative in the vicinity of apbdy to be cooled. l

11. The process of producing .refrigeration which comprises condensin a iiuoro--bromo derivative of an aliphatic ydrocarbon and then evaporating the said derivative Ain the vicinit of a body to be cooled.

12. lhe process of refrigeration which.

comprises condensing a bromo-iuoro derivative of methane and then evaporatin the said derivative in' the vicinity of a b -to be cooled. y

13. The process of refrigeration which comprises condensing monouoro-dichloro methane and then evaporating it in the vicinity of a body to be cooled.

14. The .process o refrigeration which comprises condensing a luoro-halo derivative of ethane and then'evaporating the said derivative* in the-vicinity ofv a body to be l cooled.

15. The process of .refrigeration which comprises condensing a 4luorolchloro derivative of ethane and then evaporating the said 4derivative in thevicinity of a body to be' cooled.

1'6. The 'process' of refrigeration which comprises condensing a fluoro-bromo deriva# tive of ethane and then evaporating the said derivative in the vicinity of a body to be cooled.

. 17. The process of refrigerationV which 'comprises condensing tetrailuoro-dichloro comprises condensing a halo-loro derivative` of methane and evaporating the said derivative.

' 22. The process of transferring heat which comprises condensing a. chloro-fluoro derivative of methane and evaporatingthe said dev rivative.

23. The process of transferring heat which comprises condensing a halo-fluoro derivative of ethane and then evaporating the said derivative.

24:. The process of transferring heat which comprises condensing a chloro-[luoroy derivative of ethane and then evaporating the said derivative.y v

In' testimony whereof we' aix our signatures.

THOMAS MIDGLEY. JR. .ALBERT L. HENNE. ROBERT R. McNAlY.

'lans'y asl 

